1. Field of the Invention
The present invention relates to power supply controllers controlling power supply circuits and to methods for controlling the power supply circuits.
2. Description of the Related Art
In order to output audio signals as sound from a speaker, audio apparatuses include a power amplifier circuit for amplifying sound signals and driving the speaker. Such a power amplifier circuit is supplied with power from a power supply circuit and performs amplification.
In many cases, such a power amplifier circuit has an overcurrent protection function. For example, such an overcurrent protection function stops the amplification when the volume of sound to be amplified and output reaches an excessive level and a current whose amount is larger than an acceptable amount keeps flowing in the power amplifier circuit for a predetermined time or more. Thus, destruction of the power amplifier circuit and the speaker due to the excessive amount of current is prevented.
In addition, the power supply circuit has an overcurrent protection function in order to protect the power supply circuit itself. For example, such an overcurrent protection function detects the level of a current corresponding to a load current flowing in a predetermined region of the power supply circuit. When the detected level is a predetermined value or more, the power supply circuit stops supplying power to the load. Thus, destruction of components constituting the power supply circuit due to an overcurrent flowing in accordance with an overload condition is prevented.
Accordingly, since each of a power amplifier circuit and a power supply circuit supplying power to the power amplifier circuit in an audio apparatus has an overcurrent protection function, an overcurrent protection function of a system constituted by the power amplifier circuit and the power supply circuit is further ensured. (See Japanese Unexamined Patent Application Publication Nos. 2004-56254 and 6-269159.)